The third National Health and Nutrition Examination Survey (NHANESIII) has collected descriptive data, physical measures, and biomedical samples (blood and urine) on a representative U.S. sample of children at ages two months through six years with oversampling for blacks and Mexican Americans. Serum cotinine levels were measured and information on prenatal maternal smoking obtained. Linkage of the extensive data from NHANESIII to the child's birth certificate to use the prenatal and birth information has begun. All of the states were sent requests for the relevant birth certificates with the signed permission of parents of the examined child. All certificates have been received. Computerized matching of NHANESIII and birth certificate data is underway. Results of the linkage will support research efforts to do the following: 1) To determine if low birth weight or premature children have subsequent poor health as measured by biomedical markers in a representative national sample of children through age six; 2) to assess the effects of ethnic/racial and socioeconomic factors on these outcomes; 3) to develop normative growth and other biomedical scales for a U.S. representative population, and black and Mexican-American children, according to a risk profile at birth; and 4) to develop comparisons between maternal and proxy reports of children's risk factors at birth and actual measurements for use in other studies. Analysis has begun on ear infections and respiratory outcomes in children associated with prenatal maternal smoking and current household exposures measured by serum cotinine levels.